The surface of a semiconductor substrate has conventionally been treated by one of two methods. In the first method, the surface treatment is performed with a solution that produces a chemical reaction. As a result, very little damage is caused to the substrate. However, this method is not suitable for the fine processing of semiconductor substrates, such as etching, and has not been applied in the fabrication of VLSIs except for cleaning the surfaces of semiconductor substrates.
The second most widely used method treats the surface of a substrate with a plasma. This method is broadly used in the fabrication of VLSIs, and unlike the above discussed method that uses a chemical reaction solution, plasma treatment provides fine processing, including etching, and machineability. In plasma etching, however, the plasma contains many particles and charged particles that have a high kinetic energy greater than that required for the surface treatment. These high energy particles can cause serious damage to the semiconductor substrate, and therefore the surface treatment of semiconductor substrates using a plasma is unsatisfactory in many instances.
Another method that has been proposed for treating the surfaces of semiconductor substrates is disclosed by K. Suzuki et al in the Journal of Applied Physics 64(7), Oct. 1, 1988. With this method, the semiconductor substrate surface is irradiated with a hot reactive gas that is blown in the gaseous phase at supersonic speed onto the substrate. The beam produced by this technique is used for etching and does not cause the kind of damage to the substrate surface that is caused by plasma etching. On the other hand, the beam has particles of a relatively low energy, which is insufficient for sustaining a reaction with the surface, and therefore surface treatment with this technique requires a considerable amount of time.